Coarse/fine program verification in non-volatile memory using different reference levels for improved sensing

Abstract

Coarse / fine programming of non-volatile memory is provided in which memory cells are programmed at a first rate of programming prior to reaching a coarse verify level for their intended state and a second rate of programming after reaching the coarse verify level but before reaching the final verify level for their intended state. Large sub-threshold swing factors associated with smaller memory cells can affect the accuracy of sense operations, particularly when sensing at a fine verify level after sensing at a coarse verify level without pre-charging the bit line between the different sensings. Different reference potentials are utilized when sensing at a coarse verify level and a final verify level. The different between the reference potentials can compensate for any discharge of the bit line during the coarse level sensing.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]The following application is cross-referenced and incorporated by reference herein in its entirety:[0002]U.S. patent application Ser. No. 11 / 773,035, entitled “Systems for Coarse / Fine Program Verification in Non-Volatile Memory Using Different Reference Levels for Improved Sensing,” by Shih-Chung Lee, filed concurrently.BACKGROUND OF THE INVENTION[0003]1. Field of the Invention[0004]The present disclosure relates to programming in non-volatile memory.[0005]2. Description of the Related Art[0006]Semiconductor memory devices have become more popular for use in various electronic devices. For example, non-volatile semiconductor memory is used in cellular telephones, digital cameras, personal digital assistants, mobile computing devices, non-mobile computing devices and other devices. Electrical Erasable Programmable Read Only Memory (EEPROM), including flash EEPROM, and Electronically Programmable Read Only Memory (EPROM) are among the most ...

AI Technical Summary

Benefits of technology

[0021]The technology described herein attempts to provide a more accurate sensing of the threshold voltage of non-volatile storage elements during programming verification when coarse / fine programming is utilized.

[0022]Coarse / fine programming of non-volatile memory is provided in which memory cells are programmed at a first rate of programming prior to reaching a coarse verify level for their intended state and a second rate of programming after reaching the coarse verify level but before reaching the final verify level for their intended state. Large sub-threshold swing factors associated with smaller memory cells can affect the accuracy of sense operations, particularly when sensing at a fine verify level after sensing at a coarse verify level without pre-charging the bit line between the different sensings. Different reference potentials are utilized when sensing at a coarse verify level and a final verify level. The difference between the reference potentials can compensate for any discharge of the bit line during the coarse level sensing.

Problems solved by technology

This may increase the total time needed to program the memory cells.

However, some implementations will make use of coarse / fine programming techniques when programming the highest level state as well.

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